Miniature cooling unit



May 22, 1956 F. G. KEYES MINIATURE COOLING UNIT Filed July 17. 1953INVENTOR. FREDERICK G. KEYES wzza ATTORNEYS United States PatentMINIATURE COOLING UNIT Frederick G. Keyes, Cambridge, Mass., assignor toAlfred Bicknell Associates, Inc., Cambridge, Mesa, 2 corporation ofMassachusetts Application July 17, 1953, Serial No. 368,760

7 Claims. (Cl. 62-92) The present invention relates to a miniaturerefrigeration unit and in particular to a miniature portablerefrigeration unit especially adapted for use in desensitizing skinregions in preparation for a hypodermic injection or the like.

Hypodermic injections may be made substantially painless by bringing thetemperature of the skin surrounding the area of the injection down to atemperature between freezing and 40 degrees Fahrenheit. While devicesexist which will freeze the skin for minor operations, such devices arenot useful for this purpose since freezing the skin results in anincrease in pain and sensation after the freezing wears off. If howeverthe skin is chilled to a temperature just above the freezing point, thenthe procedure is effective to eliminate all sensation both during andafter the injecting.

Accordingly, it is the object of this invention to provide a convenientand economical miniature refrigeration device which can be used quicklyand conveniently to desensitize localized areas of the skin withoutfreezing. More specifically, it is an object of the invention to providea compact self-contained refrigeration unit, capable of hand-heldoperation, which may conveniently be operated to deliver a charge ofrefrigerant to a cooling surface in contact with the skin of thepatient, so as to chill the selected skin area rapidly and effectively.It is a further object of this invention to provide such device whichwill use capsules of refrigerant in order to be completely portable andwhich will automatically meter the supply of refrigerant to theskin-contacting element as desired in amounts sufficient to effect thedesired chilling without freezing.

Other objects and features of the invention will appear from thefollowing description, taken in conjunction with the accompanyingdrawings in which Fig. 1 shows the external appearance of the device.

Fig. 2 is a sectional view taken along the major axis of the device onthe line 2-2 of Fig. 1.

Fig. 3 is a sectional view on an enlarged scale of the lower end portionof the device shown in Figs. 1 and 2, showing the heat exchange chamberand contact cooling surface of the device, and

Fig. 4 is a cross-sectional view of the heat exchange chamber, taken onthe line 4-4 of Fig. 3.

In Figs. 1 and 2 illustrating the preferred form of apparatus, the case1 is made in four sections 2, 3, 4, and 5, which are attached togetherby overlapping threaded flanges. The cap 2 fitting over the body section3 provides a chamber 9 containing a disposable metal capsule 7 ofrefrigerant. A hollow pointed needle 11 extends through the end of therefrigerant capsule and the capsule itself is firmly seated on therubber ring 13 surrounding the needle. This needle extends downward intosection 4 of the case to a small chamber 14 sealed by the O-ring 15.Refrigerant which passes through the hollow pointed needle into thischamber is filtered by the filter 19 which separates the chamber 14 fromthe passage 21 leading to the metering valve.

Patented May 22, 1956 While an ordinary needle valve would be usable,this construction is believed to provide greatly improved convenienceand economy. This valve which automatically supplies the correct amountof refrigerant consists of a valve member which in this case is a spool22 fitted so as to slide in a cylindrical chamber or cavity 20 insection 4 of the casing, and normally urged toward the head of the unitby a coil spring 24. A valve member of rectangular cross section wouldbe equally acceptable, however. In this normal position passage of therefrigerant through the duct 21 is blocked by the flange 23 of thisspool. Further sealing of the refrigerant is effected by the O-rings 25and 26 on either side of the orifice leading to the duct 21. An escapeduct 27 is provided through the case to the part of the cylindricalchamber containing the spring to prevent a building up of pressure byany refrigerant passing the O-ring 25.

The central part of the valve member is cut away to provide a recessforming a metering chamber 29 which may be loaded with refrigerant byforcing back the head of the instrument 50 causing the spool 22 tocompress the spring 24 until this metering chamber is opposite the inletport from the supply duct 21. In the normal position as shown, thismetering chamber or recess leads to an outlet port supplying thedelivery duct 31 in the case. This duct in turn leads to the annulargroove 33 cut into the lower flange 32 of the spool 22 which opens tothe delivery duct 37 carrying refrigerant to the cooling head 50 of theinstrument. This lower flange is supplied with the O-rings 35 and 36 toprevent leakage. The delivery duct 37 is surrounded by an insulatingmember 38 which serves to minimize transfer of heat from the body of theinstrument to the cooling head 54) and to firmly attach the exchanger 50with the spool 22. Contact between this insulating member and the spoolis further minimized by use of the washer 40.

The cooling head 50, construction of which will be more fully describedpresently is slidably fitted in the insulating member 41 which aprotective sleeve preventing heat transfer between the cooling head 50and the end section 5 of the case. Refrigerant which has expandedthrough the head 50 is permitted to escape through the outlet 43 in theinsulating member and then through the outlet 45 in the case.

The cooling head 50 is shown in section in Fig. 3. It consists of ahollow cylindrical shell 53 having a relatively thick flat end plate 54constructed of conductive material. The inside of this shell contains aspiral heat exchange chamber formed by a conductive vane 47 firmlyattached to the end plate 54 and extending to but not attached to theopposite end of the chamber. The refrigerant line 57 through which therefrigerant is introduced to this chamber is an extension of the supplyline 37 and is attached to the spiral vane. The refrigerant is releasedat the end and the expanding gas passes back along the spiral heatexchange chamber and the delivery line 57 to the outlet 60, which inturn leads to the exhaust port 43 described above. This use of thecounterfiow principle in a spiral chamber enables all the expandingrefrigerant to cool the incoming refrigerant in line 57 attached to thevane forming the spiral chamber. The fact that this vane is attachedfirmly on at the plate 54 provides maximum cooling of this surface whileminimizing heat flow elsewhere.

Under normal conditions the spool valve and the head are maintained inextended position shown in Fig. 2 by means of the coil spring 24, andpassage of refrigerant from the supply line 21 into the metering chamberis blocked. A capsule of liquid refrigerant is inserted in the case 3and the cap 2 is tightened down over it thus forcing the capsule againstthe seal 13 and finally forcing the needle 11 to puncture the end of thecapsule, thus releasing refrigerant through the screen 19 to the supplyline 21. The liquid refrigerant in the capsule is maintained underpressure by the vapor of the refrigerant itself which has a boilingpoint below room temperature. The preferred refrigerant for this use isdichlorodifiuorornethane commonly known in the trade as Freon 12.

When the instrument is to be used, as, for example in anesthetizing asmall area of a patients skin, the operator simply presses the head ofthe instrument 50 against a convenient surface, thus forcing the headand the spool back against the spring 24 and positioning the meteringchamber 29 opposite the inlet port from the supply duct 21 whereupon acharge of refrigerant is admitted into the metering chamber. Pressure onthe instrument is then released and the spring restores the parts to theposition shown in Fig. 2 whereupon the refrigerant is released throughthe outlet port to the delivery line 31 and into the heat exchanginghead 50. In passing through the heat exchange chamber described above,the refrigerant is vaporized and the vapor expands through this chamberthereby producing a rapid cooling effect both by absorption of thelatent heat of vaporization and by expansion. The size of the meteringchamber is such as to provide a quantity of refrigerant suflicient tocool the face of the instrument to a temperature of about 33 F.

It will be observed that this device is convenient to handle since theoperator requires only one free hand and is economical since themetering chamber supplies only the amount of refrigerant actuallyneeded. As heretofore noted it is particularly useful for mild localanesthesia for hypodermic injections. While the device has beendescribed in terms of a single embodiment it will be understood thatconsiderable variation in the actual construction may be made within thescope of this invention.

Having thus described my invention, I claim:

1. A refrigeration unit comprising a case, a detachable capsule ofcompressed refrigerant, means for tapping said capsule, valving meansfor periodically releasing a metered amount of the refrigerant, and acounterfiow heat exchanger for the refrigerant comprising a spiralchamber formed by a spiral vane attached to a flat cooling end surfacewherein the refrigerant supply is carried through said spiral chamber ina duct attached to the vane and the expanding gas escaping through thespiral cools the incoming refrigerant.

2. A refrigeration unit comprising a case, a detachable capsule ofrefrigerant, means for tapping said capsule, a valve member slidablyfitted to a chamber in the case and having a metering recess, said casehaving ducting means with an inlet port and an outlet port to thechamber separated by a distance greater than the length of the meteringrecess, spring loading means for maintaining the metering recess inregistration with the outlet port, a heat exchanger comprising a singlespiral expansion chamber for the refrigerant, ducting means connectingthe tapping means with the inlet port and the outlet port with the heatexchanger, and means for positioning the metering recess opposite theinlet port.

3. A refrigeration unit comprising a case, a removable cap fitted to thecase providing a chamber for a refrigerant capsule, a hollow needlesurrounded by a compressible sealing member in said chamber and actingin cooperation with the cap to tap the capsule, a filtering member, aduct leading from the head of the needle to the filtering member, amultiposition valve .member slidably fitted to a chamber within thecase, a metering storage recess, ducting means leading from the filterto the metering recess when the valve member is in one position, anexpansion chamber for the refrigerant, and ducting means leading fromthe storage recess to the expansion chamber when the valve is in asecond position.

4. A refrigeration unit comprising a case, a detachable capsule ofrefrigerant, means for tapping said capsule, a valve member movablyfitted to a chamber within said case whereby a metering chamber for therefrigerant is formed between the valve member and a surface of saidcase chamber, an expansion chamber having a surface to be cooled, asupply duct'from the tapping means to an inlet port for the meteringchamber, a delivery duct from an outlet port from the metering chamberto the expansion chamber, means for moving the valve member to effectflow of a charge from the inlet port to the metering chamber, and meansfor positioning the valve member to close the valve and permit 'flow ofsaid charge only from the metering chamber to the expansion chamber.

5. A refrigeration unit comprising a case, a capsule of refrigerant,means for attaching said capsule to said case, means for tapping saidcapsule, a multiposition valve member movably fitted to said case, ametering chamber, ducting means leading from the tapping means todeliver a measured charge to the metering chamber when the valve memberis in one position, an expansion chamber for the refrigerant, andducting means leading from the metering chamber to release said measuredcharge to the expansion chamber when the valve is in a second position.

6..A portable refrigerating unit comprising a case to contain adetachable capsule of compressed refrigerant, means for tapping thecapsule, a refrigerating head carried by and protruding from the caseand movable inwardly of the case, a spring normally holding the head inpro truding position, means carried by the head to form a meteringrecess, means operated by motion of the head inwardly of the case torelease a measured charge of compressed refrigerant into the meteringrecess, and a duct leading from the metering recess to the head to passthe measured charge from the metering recess and expand it into thehead.

7. A refrigeration unit comprising a case having a cavity at one end, acapsule of compressed refrigerant, means for attaching the capsule tothe case, means for tapping the capsule, a heat exchanger slidablyfitted to the end cavity of the case and having a cooling surfaceprojecting outside the case, a metering recess in the case capable ofcontaining a specified amount of refrigerant, valving means operated bycompression of the heat exchanger into the cavity to release a charge ofrefrigerant from the capsule to the metering recess, and ducting meansfor delivering the charge of refrigerant from the metering recess to.the heat exchanger.

References Cited in the file of this patent UNITED STATES PATENTS

